During the launch of Moncure Therapuetics' new flu vaccine, Mia Moncure is rocked by news that the public relations director at her family's company has been found dead in Switzerland. A cryptic video warns her that something is amiss with the vaccine, and convinces Mia that his death wasn't accidental. Determined to expose the killer, Mia heads to Lucerne, where her own life is threatened. Desperate for backup, she turns to Gio Lorenzo, communications director for a high-ranking senator, even though she's still reeling from their one-night stand months before. Mia and Gio race to uncover a deadly scheme that threatens to ruin her family's company. But time is running out. Millions of people are being vaccinated, and any of them could be the next to die.